The present invention relates to an automatic sewing machine provided with a cloth retaining device, and more particularly, to a type of such a device wherein the cloth retaining device is driven according to programmed data, so that the cloth is automatically sewn.
An automatic sewing machine which has a cloth retaining device adapted to move a cloth retainer horizontally with respect to a sewing needle which reciprocates vertically is well known. Such a cloth retaining device is widely employed for industrial sewing machines.
A conventional cloth retaining device of this type is shown in FIG. 1. A cloth retainer 12 is provided for holding the material 10 to be sewed. The cloth retainer 12 is constructed as described below. That is, one end of a lower retaining plate 16 is fixedly secured to a retainer mounting plate 14 and one end of an upper retaining plate 18 is hingedly secured to the retainer mounting plate 14 by a hinge 20 in such a manner that there is a small gap between the two plates 16 and 18. Sewing holes 16a and 18a are formed in the retaining plates 16 and 18, respectively, according to desired sewing patterns. Thus, the desired sewing patterns are formed within a zone defined by the sewing holes 16a and 18a.
The cloth retaining device has a cloth retainer driving device 22 for driving the cloth retainer 12 to predetermined positions. The device 22 has a slider 24. Slider shafts 26 and 28 are slidably inserted into the slider 24 in a manner such that the slider shafts 26 and 28 extend in the directions of the X and Y axes, respectively. The slider 24 performs sliding movement in the direction of the shafts 26,, 28 driven by means of a pulse motor (not shown). A retainer mounting stand 30 is fixedly provided on the slider 24 to install the cloth retainer 12. Positioning and holding pins 32 and 34 upstand from the upper surface of the retainer mounting stand 30. Those pins 32 and 34 are engaged with two positioning and holding holes 14a and 14b formed in the retainer mounting plate 14 of the cloth retainer 12. The cloth retainer driving device 22 thus constructed is driven by a control device (not shown) according to programmed data stored therein.
The conventional automatic sewing machine cloth retaining device is constructed as described above. Its operation will now be described.
First, the material 10 to be sewn is positioned in place between the retaining plates 16 and 18 of the cloth retainer. Then, the positioning and holding holes 14a and 14b of the cloth retainer 12 are engaged with the positioning and holding pins 32 and 34 of the cloth retainer driving device 22, respectively, so that the cloth retainer 12 is positioned and held at a predetermined position on the device 22. When a operating pedal (not shown) is operated, sewing is started whereby a desired sewing pattern is formed on the material 10 according to programmed data.
Upon the completion of sewing, the sewing machine is automatically stopped. The operator releases the engagement between the pins 32, 34 and holes 14a, 14b to remove the cloth retainer 12 from the cloth retainer driving device 22, and opens the upper retaining plate 18 to take out the material 10. Thereafter, the next piece 10 to be sewn is set in place between the retaining plates 16 and 18 of the cloth retainer 12. Similarly as in the above-described case, the cloth retainer is positioned and held by manually engaging it with the driving device 22, and sewing is again started.
The conventional cloth retaining device of the automatic sewing machine is disadvantageous in that the sewing operation is complicated and the work efficiency is low because the cloth retainer 12 must be manually engaged with or disengaged from the driving device 22 as described above. Furthermore, in the conventional device, the cloth retainer 12 is positioned in place and held merely by engaging the positioning and holding pins 32 and 34 with the positioning and holding holes 14a and 14b as described above. Therefore, during sewing the cloth retainer 12 is liable to vibrate vertically; that is, it is difficult to positively position and hold the same. This is another drawback of the conventional device.